In this Tuesday, July 24, 2012 photo, a Syrian boy sits atop a damaged military tank at the border town of Azaz, some 20 miles (32 kilometers) north of Aleppo, Syria. Turkey sealed its border with Syria to trucks on Wednesday, July 25, 2012 cutting off a vital supply line to the embattled nation as fighting stretched into its fifth day in the commercial capital of Aleppo.

The retreat of President Bashar al-Assad’s forces from parts of northeastern Syria along the Turkish border might have been welcomed by Turkey, a key supporter of the Syrian rebellion, except for one thing: The region is predominantly Kurdish, and Ankara fears the resulting power vacuum will be a major boon to its number one enemy, the Kurdistan Workers’ Party (PKK) whose three-decade separatist insurgency has seen some 40,000 people killed.

Until recently, Syria’s Kurds had been divided. A coalition of roughly a dozen Kurdish parties had tentatively backed the popular uprising against Assad, while the PKK’s Syrian ally, the Democratic Union Party (PYD), appeared to align itself with the Syrian regime, intimidating opposition activists and quashing popular protests. Others sat on the sidelines, wary of closing ranks with a Sunni Arab-dominated opposition that turned a deaf ear to Kurdish demands for new rights in a post-Assad Syria. Two weeks ago – perhaps sensing that the regime’s fall was imminent – the rival Syrian Kurdish political currents put aside their differences, under the coaching of Iraqi Kurdish leader Massoud Barzani. In Irbil, capital of Iraq’s autonomous Kurdish Regional Government, they signed a unity agreement that has allowed them to take control of several northeastern towns, Assad’s forces mostly retreating without a fight.

The news sparked a Turkish media and political clamor about the imminent rise of a “PKK Republic” or a “Western Kurdistan” on Turkey’s southern flank. Commentators fear that the rise of a second Kurdish statelet, following the emergence of the one in neighboring Iraq in 2003, would embolden Turkey’s own 12-15 million Kurds to pursue their own dream of autonomy. Worse still, it could potentially provide the PKK — branded as a terrorist organization by Turkey, the U.S., and the EU — with sanctuaries from which to launch cross-border attacks.

Picking up where the media left off, Turkey’s fiery leader, Prime Minister Recep Tayyip Erdogan, banged the war drums. Though he and his government proclaim the Kurds a “brother nation,” Erdogan told a TV interviewer on Wednesday, a Kurdish state in northern Syria would likely become a “terrorist entity”. If need be, he warned, Turkey would not hesitate to hit the PKK inside Syria, as it has done repeatedly in northern Iraq. “If a formation that’s going to be a problem emerges, if there is a terror operation, an irritant, then intervening would be our most natural right.”

It would not be easy. In northern Iraq — where the PKK has come under pressure from a Barzani government that seeks to improve ties with Ankara — the rebels remain ensconced in remote mountain hideouts, making it easier for Turkish forces to target them with relative impunity. In Syria, the PKK-aligned PYD is an urban-based outfit. To bring the fight to them, Turkish troops would have to operate in large population centers, many of them within a stone’s throw of the common border.

Syrian Kurds are quick to counter Turkish alarmism. Ankara is overstating the PKK’s influence in Syria, Abdulhalim, a Kurdish activist in Syria, told TIME via Skype. Even if it is the strongest and best armed of the Kurdish factions in Syria, the PYD is in no position to overwhelm its local rivals. “People will not allow the PYD to control the area,” Abdulhalim insists. “All people here, Arabs, Christians, and other ethnicities, will be in control.” The radicals would also have to contend with Barzani, whose government has provided training to Kurdish defectors from Assad’s army.

But, Abdulhalim warns, nothing would unite the Kurds of Syria more than resistance to a Turkish incursion. “We are strongly refusing Erdogan talking about any invasion of Syria to protect Turkey from the PYD,” he says.

When the sabre-rattling dies down, writes Oral Calislar, a commentator for Radikal, a Turkish newspaper, Ankara will do the same with a Kurdish quasi-state in Syria as it did with the one in Iraq – learn to live with it. “We used to say we’d never tolerate an autonomous Kurdistan on our border,” Calislar writes. “It was one of our ‘red lines.’ And now we’re buddy-buddy with Barzani.”

For the time being, the most that Turkey can do to contain the fallout from Syria is to make amends with its own Kurds, says Hugh Pope, an analyst with the International Crisis Group. If Erdogan wants to ensure Turkey’s security, he adds, his government will have to do so by addressing the Turkish Kurds’ main grievances – adequate political representation, mother tongue education, some degree of devolution, and a partial amnesty for PKK members.

The situation across the border might be “alarming” for Turkey, says Pope, “but only because Turkey has not solved its own Kurdish problem.”